Eye optical characteristic measuring instrument

ABSTRACT

Scattering can be measured by using an optical system having a Hartman-Shack wave-surface sensor. An eye optical characteristic measuring instrument comprises a light source unit ( 10 ) for emitting a light beam of a wavelength in the near-infrared region, an illumination optical system ( 40 ) for illuminating a small area of the retinal of an eye to be measured with the light beam from the light

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an eye optical characteristic measuringapparatus for measuring eye optical characteristics.

2. Description of the Related Art

Since a Hartmann-Shack wavefront sensor can accurately measure wavefrontaberrations of an eye, it has recently attracted considerable attention.This wavefront sensor can become a necessary apparatus in eye surgery innear future especially for the purpose of the planning and follow-up ofcornea refractive surgery.

The measurement of the eye wavefront aberrations by the wavefront sensoris greatly different from the measurement of corneal wavefrontaberrations by corneal shape measurement in that the measurement resultincludes an influence of an intraocular optical system, such as acrystalline lens, on the wavefront aberrations. According to thisfunction, it becomes possible to perform an examination in a case wherethe crystalline lens has refractive index abnormality due to nuclearcataract or the like or in a case where the shape of a refractive planeof the crystalline lens is largely distorted by lenticonus.

As an object of the eye optical system wave front aberrationsmeasurement, an objective evaluation of visual functions can be named.As the evaluation of the visual functions, a subjective examination hasbeen conventionally recognized as a reliable measurement method ascompared with an objective examination. Especially, this is true to suchan extent that with respect to an auto-refractometer as a formerwavefront sensor, a lens interchange method as the subjectiveexamination is called a gold standard.

When the eye wavefront aberrations measured by the wavefront sensor iscompared with corrected eyesight or contrast sensitivity, there is acase where they are fully coincident to each other, and there is a casewhere they are not coincident to each other especially in, for example,old people. In the case of the inconsistency, there is a case wherescattering has a large effect on the eyesight.

SUMMARY OF THE INVENTION

As optical factors to influence the visual functions, scattering of aneye optical system, together with the wavefront aberrations, isconceivable.

In the measurement of eye optical characteristics, in the case of aging,cataract, or the like, light scattering from an eye optical system islarge, and for the purpose of the objective evaluation of the visualfunctions, measurement of the light scattering is necessary in additionto the aberrations. An apparatus is desired which enables simultaneousmeasurement of the light scattering by an optical system of aHartmann-Shack wavefront sensor which has an established reputation inmeasurement of the wavefront aberrations. On the other hand, thewavefront aberrations measurement by the Hartmann-Shack wavefront sensoris already in practical use.

In view of the above, the present invention has an object to provide aneye optical characteristic measuring apparatus which can accuratelyevaluate visual functions by enabling a Hartmann-Shack wavefront sensor,which has a main object of performing wavefront aberrations measurement,to perform light scattering measurement and by performing the lightscattering measurement.

Besides, the invention has an object to provide an eye opticalcharacteristic measuring apparatus which enables simultaneousmeasurement of scattering of the eye by an optical system of theHartmann-Shack wavefront sensor by developing, as a scatteringmeasurement method by the Hartmann-Shack wavefront sensor, a scatteringanalytic method for estimating a scattering amount from SIR (ScatterIntensity Ratio) of background light of a Hartmann image.

Besides, the invention has an object to provide an eye opticalcharacteristic measuring apparatus which can measure wavefrontaberrations of a light flux incident on a light receiving optical systemand a scattering degree of a received light flux from a distribution ofrelations between the wavefront aberrations of the light flux incidenton the light receiving optical system and a point spread function (PSF)of the received light.

Besides, the invention has an object to provide an eye opticalcharacteristic measuring apparatus which can judge that from adistribution of relations between wavefront aberrations of a light fluxincident on a light receiving optical system, a scattering degree of areceived light flux and a spot diameter of the received light flux, asthe wavefront aberrations of the light flux incident on the lightreceiving optical system and the scattering degree of the received lightflux become high, or as the spot diameter of the received light fluxbecomes large, an influence of cataract or the like becomes large.

In order to achieve the above objects, according to first solving meansof the invention, an eye optical characteristic measuring apparatusincludes a light source part for emitting a light flux having aspecified wavelength, an illumination optical system for illuminating aminute area on a retina of a subject eye with the light flux from thelight source part, a light receiving optical system for receiving a partof a reflected light flux of the light flux emitted from the lightsource part and reflected by the retina of the subject eye through aconversion member for converting it into at least substantially 17beams, a light receiving part for receiving a received light flux guidedby the light receiving optical system to form a signal, and anarithmetic part for obtaining wavefront aberrations of the light fluxincident on the light receiving optical system and a scattering degreeof the received light flux on the basis of the signal from the lightreceiving part.

Besides, according to second solving means of the invention, an eyeoptical characteristic measuring apparatus includes a light source partfor emitting a light flux having a specified wavelength, an illuminationoptical system for illuminating a minute area on a retina of a subjecteye with the light flux from the light source part, a light receivingoptical system for receiving a part of a reflected light flux of thelight flux emitted from the light source part and reflected by theretina of the subject eye through a conversion member for converting itinto at least substantially 17 beams, a light receiving part forreceiving a received light flux guided by the light receiving opticalsystem to form a signal, and an arithmetic part for obtaining wavefrontaberrations of the light flux incident on the light receiving opticalsystem and a spot diameter of the received light flux on the basis ofthe signal from the light receiving part.

Besides, according to the invention, in the eye optical characteristicmeasuring apparatus of the first solving means, the arithmetic part canobtain a distribution of relations between the wavefront aberrations ofthe light flux incident on the light receiving optical system and thescattering degree of the received light flux. Further, according to theinvention, in the eye optical characteristic measuring apparatus asstated above, the arithmetic part can be constructed to judge that asthe obtained wavefront aberrations of the light flux incident on thelight receiving optical system and the scattering degree of the receivedlight flux become high, the influence of cataract or the like becomeslarge.

Besides, according to the invention, in the eye optical characteristicmeasuring apparatus of the second solving means, the arithmetic part canobtain a distribution of relations between the wavefront aberrations ofthe light flux incident on the light receiving optical system and thespot diameter of the received light flux. Further, according to theinvention, in the eye optical characteristic measuring apparatus asstated above, the arithmetic part can be constructed to judge that asthe obtained wavefront aberrations of the light flux incident on thelight receiving optical system and the spot diameter of the receivedlight flux become large, the influence of cataract or the like becomeslarge.

Besides, according to the invention, in the eye optical characteristicmeasuring apparatus of the first solving means, the arithmetic part canobtain a distribution of relations among the wavefront aberrations ofthe light flux incident on the light receiving optical system, thescattering degree of the received light flux, and a spot diameter of thereceived light flux. Further, according to the invention, in the eyeoptical characteristic measuring apparatus as stated above, thearithmetic part can be constructed to judge that as the obtainedwavefront aberrations of the light flux incident on the light receivingoptical system and the scattering degree of the received light fluxbecome high, or the spot diameter of the received light flux becomeslarge, the influence of the cataract or the like becomes large.

Further, according to the invention, a display part for displaying thedistribution obtained by the arithmetic part, the judgment result andthe like, or an output part for outputting them to the outside may beincluded.

Further, according to third solving means of the invention, an eyeoptical characteristic measuring apparatus includes a light source partfor emitting a light flux having a specified wavelength, an illuminationoptical system for illuminating a minute area on a retina of a subjecteye with the light flux from the light source part, a light receivingoptical system for receiving a part of a reflected light flux of thelight flux emitted from the light source part and reflected by theretina of the subject eye through a conversion member for converting itinto at least substantially 17 beams, a light receiving part forreceiving a received light flux guided by the light receiving opticalsystem to form a signal, and an arithmetic part for obtaining a pointspread function obtained from wavefront aberrations of the light fluxincident on the light receiving optical system and an actually measuredspot diameter of the received light flux on the basis of the signal fromthe light receiving part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a schematic optical system 100 of an eyeoptical characteristic measuring apparatus of the invention.

FIG. 2 is a structural view of a Placido disk.

FIG. 3 is a block diagram showing a schematic electrical system 200 ofthe eye optical characteristic measuring apparatus of the invention.

FIG. 4 is a detailed structural view relating to an arithmetic part ofthe eye optical characteristic measuring apparatus of the invention.

FIG. 5 is a view in which a part of an image received by a first lightreceiving part 23 is enlarged.

FIG. 6 is an explanatory view for obtaining a point spread function froma wavefront.

FIG. 7 is a view (1) of experimental results according to an eye opticalcharacteristic measuring apparatus of an embodiment.

FIG. 8 is a view (2) of experimental results according to the eyeoptical characteristic measuring apparatus of the embodiment.

FIG. 9 is an explanatory view showing a picture of point images andpoint image intensity.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the drawings.

1. Explanation of Principle of Eye Optical Characteristic Measurement

FIG. 1 is a view roughly showing an optical system 100 of an eye opticalcharacteristic measuring apparatus of the invention.

The optical system 100 of the eye optical characteristic measuringapparatus is an apparatus for measuring, for example, an opticalcharacteristic of an eye 60 to be measured as an object, and includes afirst illuminating optical system 10, a first light receiving opticalsystem 20, a second light receiving optical system 30, a common opticalsystem 40, an adjusting optical system 50, a second illuminating opticalsystem 70, and a second light sending optical system 80. Incidentally,with respect to the eye 60 to be measured, a retina 61 and a cornea 62are shown in the drawing.

The first illuminating optical system 10 includes, for example, a firstlight source part 11 for emitting a light flux of a first wavelength,and a condensing lens 12, and is for illuminating a minute region on theretina (eyeground) 61 of the eye 60 to be measured with the light fluxfrom the first light source part 11 so that its illumination conditioncan be suitably set. Incidentally, here, as an example, the firstwavelength of the illuminating light flux emitted from the first lightsource part 11 is a wavelength of an infrared range (for example, 780nm). It is not limited to the wavelength, a illuminating light flux of aspecified wavelength can be used.

Besides, it is desirable that the first light source part 11 has a largespatial coherence and a small temporal coherence. Here, the first lightsource part 11 is, for example, a super luminescence diode (SLD), and apoint light source having high luminescence can be obtained.

Incidentally, the first light source part 11 is not limited to the SLD,and for example, a laser having a large spatial coherence and a largetemporal coherence can also be used by combining a rotary prismdescribed later. Further, an LED having a small spatial coherence and asmall temporal coherence can also be used, if light quantity issufficient, by inserting, for example, a pinhole or the like at aposition of a light source in an optical path.

Besides, in order to uniform the irregular characteristics of reflectedlight from the retina, a wedge-shaped rotary prism (D prism) 16 isinserted in the illumination optical system. Since an illuminatedportion on the retina is operated by the rotation of the rotary prism,the reflected light from the retina becomes uniform, and it is possibleto uniform the received light flux (point image) of the light receivingpart.

The first light receiving optical system 20 includes, for example, acollimator lens 21, a Hartmann plate 22 as a conversion member forconverting a part of a light flux (first light flux) reflected andreturned from the retina 61 of the eye 60 to be measured into at least17 beams, and a first light receiving part 23 for receiving the pluralbeams converted by the Hartmann plate 22, and is for guiding the firstlight flux to the first light receiving part 23. Besides, here, a CCDwith little readout noise is adopted for the first light receiving part23, and as the CCD, a suitable type of CCD, for example, a general lownoise type of CCD, a cooling CCD of 1000*1000 elements for measurement,or the like can be applied.

The second illuminating optical system 70 includes a second light source72 and a Placido's disk 71. Incidentally, the second light source 72 canbe omitted. FIG. 2 shows an example of a structural view of thePlacido's disk. The Placido's disk 71 is for projecting an index of apattern composed of plural co-axial rings. Incidentally, the index ofthe pattern composed of the plural co-axial rings is an example of anindex of a specified pattern, and a different suitable pattern can beused. Then, after an alignment adjustment described later is completed,the index of the pattern composed of the plural co-axial rings can beprojected.

The second light sending optical system 80 is for mainly performing, forexample, the alignment adjustment described later, and measurement andadjustment of a coordinate origin and a coordinate axis, and includes asecond light source part 31 for emitting a light flux of a secondwavelength, a condensing lens 32, and a beam splitter 33.

The second light receiving optical system 30 includes a condensing lens34 and a second light receiving part 35. The second light receivingoptical system 30 guides a light flux (second light flux), which isoriginated from the pattern of the Placido's disk 71 illuminated fromthe second illuminating optical system 70 and is reflected and returnedfrom the anterior eye part or the cornea 62 of the eye 60 to bemeasured, to the second light receiving part 35. Besides, it can alsoguide a light flux, which is emitted from the second light source part31 and is reflected and returned from the cornea 62 of the eye 60 to bemeasured, to the second light receiving part 35. Incidentally, as thesecond wavelength of the light flux emitted from the second light sourcepart 31, for example, a wavelength different from the first wavelength(here, 780 nm) and longer than that (for example, 940 nm) can beselected.

The common optical system 40 is disposed on an optical axis of the lightflux emitted from the first illuminating optical system 10, can beincluded in the first and the second illuminating optical systems 10 and70, the first and the second light receiving optical systems 20 and 30,the second light sending optical system 80 and the like in common, andincludes, for example, an a focal lens 42, beam splitters 43 and 45, anda condensing lens 44. The beam splitter 43 is formed of such a mirror(for example, a polarization beam splitter) that the wavelength of thesecond light source part 31 is sent (reflected) to the eye 60 to bemeasured, the second light flux reflected and returned from the retina61 of the eye 60 to be measured is reflected, and the wavelength of thefirst light source part 11 is transmitted. The beam splitter 45 isformed of such a mirror (for example, a dichroic mirror) that thewavelength of the first light source part 11 is sent (reflected) to theeye 60 to be measured, and the first light flux reflected and returnedfrom the retina 61 of the eye 60 to be measured is transmitted. By thebeam splitters 43 and 45, the first and the second light fluxes do notmutually enter the other optical systems to generate noise.

The adjusting optical system 50 is for mainly performing, for example, aworking distance adjustment described later, includes a third lightsource part 51, a fourth light source part 55, condensing lenses 52 and53, and a third light receiving part 54, and is for mainly performingthe working distance adjustment.

Next, the alignment adjustment will be described. The alignmentadjustment is mainly carried out by the second light receiving opticalsystem 30 and the second light sending optical system 80.

First, the light flux from the second light source part 31 illuminatesthe eye 60 to be measured as the object with the substantially parallellight flux through the condensing lens 32, the beam splitters 33 and 43,and the afocal lens 42. The reflected light flux reflected by the cornea62 of the eye 60 to be measured is emitted as a divergent light fluxsuch as is emitted from a point at the half of the radius of curvatureof the cornea 62. The divergence light flux is received as a spot imageby the second light receiving part 35 through the afocal lens 42, thebeam splitters 43 and 33, and the condensing lens 34.

Here, in the case where the spot image on the second light receivingpart 35 deviates from the optical axis, the main body of the eye opticalcharacteristic measuring apparatus is moved and adjusted vertically andhorizontally, and the spot image is made to coincide with the opticalaxis. As stated above, when the spot image coincides with the opticalaxis, the alignment adjustment is completed. Incidentally, with respectto the alignment adjustment, the cornea 62 of the eye 60 to be measuredis illuminated by the third light source 51, and an image of the eye 60to be measured obtained by this illumination is formed on the secondlight receiving part 35, and accordingly, this image may be used to makethe pupil center coincide with the optical axis.

Next, the working distance adjustment will be described. The workingdistance adjustment is mainly carried out by the adjusting opticalsystem 50.

First, the working distance adjustment is carried out by, for example,irradiating the eye 60 to be measured with a parallel light flux emittedfrom the fourth light source part 55 and close to the optical axis, andby receiving the light reflected from the eye 60 to be measured throughthe condensing lenses 52 and 53 by the third light receiving part 54.Besides, in the case where the eye 60 to be measured is in a suitableworking distance, a spot image from the fourth light source part 55 isformed on the optical axis of the third light receiving part 54. On theother hand, in the case where the eye 60 to be measured is out of thesuitable working distance, the spot image from the fourth light sourcepart 55 is formed above or below the optical axis of the third lightreceiving part 54. Incidentally, since the third light receiving part 54has only to be capable of detecting a change of a light flux position onthe plane containing the fourth light source part 55, the optical axisand the third light receiving part 54, for example, a one-dimensionalCCD arranged on this plane, a position sensing device (PSD) or the likecan be applied.

Next, a positional relation between the first illuminating opticalsystem 10 and the first light receiving optical system 20 will beroughly described.

The beam splitter 45 is inserted in the first light receiving opticalsystem 20, and by this beam splitter 45, the light from the firstilluminating optical system 10 is sent to the eye 60 to be measured, andthe reflected light from the eye 60 to be measured is transmitted. Thefirst light receiving part 23 included in the first light receivingoptical system 20 receives the light transmitted through the Hartmannplate 22 as the conversion member and generates a received light signal.

Besides, the first light source part 11 and the retina 61 of the subjecteye 60 form a conjugated relation. The retina 61 of the subject eye 60and the first light receiving part 23 are conjugated. Besides, theHartmann plate 22 and the pupil of the subject eye 60 form a conjugatedrelation. Further, with respect to the first light receiving opticalsystem 20, the cornea 62 as the anterior eye part of the subject eye 60and the pupil, and the Hartmann plate 22 form a substantially conjugatedrelation. That is, the front focal point of the afocal lens 42 issubstantially coincident with the cornea 62 as the anterior eye part ofthe subject eye 60 and the pupil. Besides, the plane of the rotary prism16 inclined with respect to the optical axis is disposed at asubstantially conjugated position with respect to the pupil.

Besides, the first illuminating optical system 10 and the first lightreceiving optical system 20 are moved together so that a signal peak bythe reflected light at the first light receiving part 23 becomes maximumon the condition that the light flux from the first light source part 11is reflected at a point on which it is condensed. Specifically, thefirst illuminating optical system 10 and the first light receivingoptical system 20 are moved in a direction in which the signal peak atthe first light receiving part 23 becomes large, and are stopped at aposition where the signal peak becomes maximum. By this, the light fluxfrom the first light source part 11 is condensed on the eye 60 to bemeasured.

The lens 12 converts a diffused light of the light source 11 into aparallel light. A diaphragm 14 is positioned at an optically conjugatedposition with respect to the pupil of the eye or the Hartmann plate 22.The diaphragm 14 has a diameter smaller than an effective range of theHartmann plate 22, and the so-called single path aberrations measurement(method in which the aberrations of the eye has an influence on only thelight receiving side) is established. In order to satisfy the above, thelens 13 is disposed such that the conjugated point of the retina of thereal light beam coincides with the front focal position, and further, inorder to satisfy the conjugated relation between the lens and the pupilof the eye, it is disposed such that the rear focal position coincideswith the diaphragm 14.

Besides, after a light beam 15 comes to have a light path common to alight beam 24 by the beam splitter 45, it travels in the same way as thelight beam 24 paraxially. However, in the single path measurement, thediameters of the light beams are different from each other, and the beamdiameter of the light beam 15 is set to be rather small as compared withthe light beam 24. Specifically, the beam diameter of the light beam 15is, for example, about 1 mm at the pupil position of the eye, and thebeam diameter of the light beam 24 can be about 7 mm (incidentally, inthe drawing, the light beam 15 from the beam splitter 45 to the retina61 is omitted).

Next, the Hartmann plate 22 as the conversion member will be described.

The Hartmann plate 22 included in the first light receiving opticalsystem 20 is a wavefront conversion member for converting a reflectedlight flux into plural beams. Here, plural micro-Fresnsel disposed on aplane orthogonal to the optical axis are applied to the Hartmann plate22. Besides, in general, with respect to the measuring object part (theeye 60 to be measured), in order to measure a spherical component of theeye 60 to be measured, a third-order astigmatism, and other higher orderaberrations, it is necessary to perform the measurement with at least 17beams through the eye 60 to be measured.

The micro-Fresnel lens is an optical element, and includes, for example,a ring with a height pitch for each wavelength, and a blade optimizedfor emission parallel to a condensing point. The micro-Fresnel lens hereis subjected to, for example, 8-level optical path length variationemploying a semiconductor fine working technique, and achieves a highcondensing efficiency (for example, 98%).

Besides, the reflected light from the retina 61 of the eye 60 to bemeasured passes through the afocal lens 42 and the collimate lens 21,and is condensed on the first light receiving part 23 through theHartmann plate 22. Accordingly, the Hartmann plate 22 includes awavefront conversion member for converting the reflected light flux intoat least 17 beams.

FIG. 3 is a block diagram roughly showing an electrical system 200 ofthe eye optical characteristic measuring apparatus of the invention. Theelectrical system 200 of the eye optical characteristic measuringapparatus includes, for example, an arithmetic part 210, a control part220, a display part 230, a memory, 240, a first driving part 250, and asecond driving part 260.

The arithmetic part 210 receives a received light signal (first) (4)obtained from the first light receiving part 23, a received light signal(second signal) (7) obtained from the second light receiving part 35,and a received light signal (10) obtained from the third light receivingpart 54, and performs an arithmetical operation on the origin ofcoordinates, a coordinate axis, movement of coordinates, rotation,ocular aberrations, corneal higher order aberrations, Zernikecoefficients, aberration coefficients, a Strehl ratio, a white lightMTF, a Landolt's ring pattern and the like. Besides, signalscorresponding to such calculation results are outputted to the controlpart 220 for performing the whole control of an electric driving system,the display part 230, and the memory 240, respectively. Incidentally,the details of the arithmetic part 210 will be described later.

The control part 220 controls lighting and lights-out of the first lightsource part 11 on the basis of the control signal from the arithmeticpart 210, or controls the first driving part 250 and the second drivingpart 260. For example, on the basis of the signals corresponding to theoperation results in the arithmetic part 210, the control part outputs asignal (1) to the first light source part 11, outputs a signal (5) tothe Placido's disk 71, outputs a signal (6) to the second light sourcepart 31, outputs a signal (8) to the third light source part 51, outputsa signal (9) to the fourth light source part 55, and outputs signals tothe first driving part 250 and the second driving part 260.

The first driving part 250 is for moving the whole first illuminatingoptical system 10 in the optical axis direction on the basis of, forexample, the received light signal (4) inputted to the arithmetic part210 from the first light receiving part 23, and outputs a signal (2) toa not-shown suitable lens movement means and drives the lens movementmeans. By this, the first driving part 250 can perform the movement andadjustment of the first illuminating optical system 10.

The second driving part 260 is for moving the whole first lightreceiving optical system 20 in the optical axis direction on the basisof, for example, the received light signal (4) inputted to thearithmetic part 210 from the first light receiving part 23, and outputsa signal (3) to a not-shown suitable lens movement means, and drives thelens movement means. By this, the second driving part 260 can performthe movement and adjustment of the first light receiving optical system20.

FIG. 4 is a detailed structural view concerning the arithmetic part ofthe eye optical characteristic measuring apparatus of the invention. Thearithmetic part 210 includes a measurement part 111, an analysis part111′, a coordinate setting part 112, an alignment control part 113, amarker setting part 114, an input/output part 115, and a conversion part116.

The first light receiving part 23 forms a first received light signalfrom a received light flux reflected and returned from the retina of thesubject eye and guides it to the measurement part 111. The second lightreceiving part 35 forms a second received light signal includinginformation of the anterior eye part from the received light fluxincluding information relating to the feature portion of the anterioreye part of the subject eye and/or a marker formed at the anterior eyepart of the subject eye, and guides it to the measurement part 111 andthe coordinate setting part 112.

The measurement part 111 obtains the optical characteristics includingthe refractive power of the subject eye or the corneal formation on thebasis of the first received light signal from the first light receivingpart. Besides, the measurement part 111 sends the first received lightsignal to the analysis part 111′ for obtaining the spot diameter of thereceived light flux and the scattering degree of the received lightflux. Incidentally, the analysis part 111′ may be constructed so as todirectly receive the first received light signal from the first lightreceiving part 23. The details of the analysis part 111′ will bedescribed later. The measurement part 111 performs the eye opticalcharacteristic measurement especially on the basis of the first receivedlight signal from the first light receiving part 23. Besides, themeasurement part 111 performs the cornea topography measurementespecially on the basis of the second received light signal from thesecond light receiving part 35. Besides, the measurement part 111performs calculation of aberrations results, and calculation of anaberration amount as the need arises, and outputs the calculationresults to a surgical apparatus through the output part 115.

FIG. 5 is a view in which a part of an image received by the first lightreceiving part 23 is enlarged. The drawing (A) shows a keratoconic eye,and the drawing (B) shows an example of a Hartmann image in the case ofa cataractous eye. The Hartmann image received by the first lightreceiving part 23 is, for example, the image on the basis of thereflected light from the subject eye, and includes plural area points(circles, ellipses, etc. in the drawing) in the case where the reflectedlight is received onto the first light receiving part 23 as light fluxesdiffused generally outward through the Hartmann plate 22. An opticalsignal of the Hartmann image in this example is converted into anelectrical signal, and is inputted (or captured) as the first signal tothe analysis part 111′.

As stated above, the information from the Hartmann-Shack wavefrontsensor includes the following.

Wavefront from the barycenter of the point image (classical aberrationmeasurement).

Local information from the blur degree of the point image (localscattering measurement).

Besides, with respect to the eye with much scattering, the blur of animage which can not be explained from only the wavefront aberrations areobserved in the Hartmann image. Besides, it is conceivable that thescattering amount is estimated by comparing the Hartmann image obtainedby the measurement with the Hartmann image restored from the wavefrontaberrations.

The analysis part 111′ regards the plural area points as one of thereceived light fluxes, and obtains the spot diameter of the receivedlight flux and the ratio of the maximum value of the light amount of thereceived light flux to the minimum value, that is, the scattering degreeof the received light flux. The analysis part 111′ obtains thedistribution indicating the relation between the wavefront aberrationsof the light flux incident on the light receiving optical system and thescattering degree of the received light flux. Besides, it obtains thedistribution indicating the relation between the wavefront aberrationsof the light flux incident on the light receiving optical system and thespot diameter of the received light flux. Incidentally, since theanalysis part 111′ obtains the distribution concerning the correlationamong the wavefront aberrations of the light flux incident on the lightreceiving optical system, the catering degree of The received lightflux, and the spot diameter of the received light flux, a limitation isnot made to the foregoing distribution.

The analysis part 111′ obtains the point spread function (PSF) by waveoptical calculation from the wavefront aberrations of the light fluxincident on the light receiving system, and has a calculation functionto compare this with the diameter of the received light flux, that is,the point spread function (PSF) obtained by actually measuring theintensity from the image. For example, there is also a case where acomparison can be made concerning an area at an intermediate valuebetween a maximum value and a minimum value in a square area (length ofits side is almost equal to the interval of point images and one pointimage is generally contained in this area) including the point image, awidth or the like.

Incidentally, the foregoing analysis of the analysis part 111′ maycorrespond to plural specified point images of the Hartmann image, andin this condition, as the result of one measurement, the respectivepoint images may be analyzed in the calculation, or an average value ofactually measured values may be used.

The analysis part 111′ judges that as the obtained scattering degree ofthe received light flux of the light flux incident on the lightreceiving optical system as the first light receiving part becomes high,the influence of the cataract or the like becomes large, and can outputthat to the display part 240. Besides, the analysis part 111′ judgesthat as the obtained spot diameter of the received light flux in thelight receiving optical system as the first light receiving part becomeslarge, the influence of the cataract or the like becomes large, and canoutput that to the display part 240.

Incidentally, the judgment result, analysis result and the like by theanalysis part 111′ may be displayed in various forms, such as data,table, graph, three-dimensional display and graphic, on the display part240, or may be outputted to a recording medium, such as a CD-ROM, a FDor an MO, or another apparatus by the output part.

FIG. 6 is an explanatory view for obtaining the point spread functionfrom the wavefront.

The wavefront of the light flux reflected from the retina of the subjecteye passes through the Hartmann plate, and the wavefront aberrations RMSin a lenslet are obtained from the inclination of the light flux at thattime, and a factor such as an area of a half-value portion of the pointspread function PSF is obtained.

Incidentally, the analysis part 111′ can obtain a scattering coefficientin a manner as indicated by a following expression.Index={square root}{square root over (A)}−(a·RMS _(SL) −c)  (1)

-   Index: scattering prediction coefficient (also called scattering    prediction index)-   A: area (average) of the half-value portion of the PSF-   RMS_(SL): wavefront aberrations (average) in the lenslet portion-   a: constant obtained by non-cataractous eye measurement-   c: scattering correction constant of measuring apparatus.

Incidentally, a and c are coefficients of a regression line obtained inFIG. 7 by using a keratoconic eye and a normal eye. In this case, a:first-order coefficient of 28.894, and c constant term of 8.6623.

In the actual analysis, there is also a case where the area A isobtained for the plural point images of the Hartmann image, this issubjected to the processing of the above expression and is averaged toobtain the result of one measurement.

This scattering coefficient is obtained for the respective lenslets byusing various factors of the respective lenslets.

The relation between the picture of the point image and the point imageintensity is as shown in FIG. 9. At this time, when such a CCD that agamma value indicating a relation between a light amount and an outputbecomes 1 is adopted, since the intensity distribution of the PSF isproportional to the digital count (computer count) of the CCD, themeasurement is easy. Here, the minimum intensity and the maximumintensity are obtained in a quadrangle 0.6 mm square with the pointimage as the center, and a son contrast ratio can also be obtained fromthis, and an area at an intermediate point between the minimum intensityand the maximum intensity can also be obtained.

Besides, a method is also conceivable in which instead of the wavefrontaberrations RMS_(SL), the point spread function (PSF) of FIG. 6 isobtained from the wavefront aberrations by calculation, and this iscompared with the actually measured PSF.

In the case where this method is used, it becomes unnecessary to makethe correction using the eye with little scattering, such as the normaleye or the keratoconus, and the reliability of the result is increased.On the other hand, in the former method in which the wavefrontaberrations and the PSF are compared with each other, since there is notrouble to calculate the PSF by calculation, the total processing timecan be made considerably short.

The coordinate setting part 112 converts signals of a first and a secondcoordinate systems corresponding to the pupil of the subject eyeincluded in the first and the second received light signals into signalsof reference coordinate systems, respectively. The coordinate settingpart 112 obtains a pupil edge and a pupil center on the basis of therespective signals of the first and the second coordinate systems.

Besides, the coordinate setting part 112 decides the origin ofcoordinates and the direction of a coordinate axis on the basis of thesecond received light signal including feature signals of the anterioreye part of the subject eye. Besides, the coordinate setting part 112obtains the origin of the coordinates, and the rotation and movement ofthe coordinate axis on the basis of at least one of the feature signalsof the anterior eye part of the subject eye of the second received lightsignal, and correlates the measurement data with the coordinate axis.Incidentally, the feature portion includes at least one of a pupilposition, a pupil center, a corneal center, an iris position, an irispattern, a pupil shape, and a limbus shape. For example, the coordinatesetting part 112 sets the origin of the coordinates, such as the pupilcenter or the corneal center. The coordinate setting part 112 forms thecoordinate system on the basis of the feature signal corresponding tothe image of the feature portion of the anterior eye part of the subjecteye included in the second received light signal. Besides, thecoordinate setting part 112 forms the coordinate system on the basis ofa marker signal included in the second received light signal andconcerning a marker provided on the subject eye, and a signal concerningthe anterior eye part of the subject eye. The coordinate setting part112 can decide the origin of the coordinates and the direction of thecoordinate axis on the basis of the second received light signalincluding the marker signal. The coordinate setting part 112 obtains theorigin of the coordinates on the basis of the marker signal in thesecond received light signal, obtains the rotation and movement of thecoordinate axis on the basis of any one of the feature signals of theanterior eye part of the subject eye in the second received lightsignal, and can correlate the measurement data with the coordinate axis.Alternatively, the coordinate setting part 112 obtains the origin of thecoordinates on the basis of at least one of the feature signalsconcerning the anterior eye part in the second received light signal,obtains the rotation and movement of the coordinate axis on the basis ofthe marker signal in the second received light signal, and may correlatethe measurement data with the coordinate axis. Alternatively, thecoordinate setting part 112 obtains the origin of the coordinates andthe rotation and movement of the coordinate axis on the basis of atleast one of the feature signals of the anterior eye part of the subjecteye in the second received light signal, and may correlate themeasurement data with the coordinate axis.

The conversion part 116 correlates the first and the second opticalcharacteristics of the subject eye obtained by the measurement part 111through the respective reference coordinate systems formed by thecoordinate setting part and combines them. Besides, the conversion part116 performs conversion to the reference coordinate system by making thepupil center obtained by the coordinate setting part 112 the origin.

One of, two or more of, or all of the first illuminating optical system10, the first light receiving optical system 20, the second lightreceiving optical system 30, the common optical system 40, the adjustingoptical system 50, the second illuminating optical system 70, and thesecond light sending optical system 80 are suitably provided in analignment part of the optical system 100. The alignment control part 113can move this alignment part according to the movement of the subjecteye and in accordance with the operation result of the coordinatesetting part 112 on the basis of the second received light signalobtained by the second light receiving part. On the basis of thecoordinate system set by the coordinate setting part 112, the markersetting part 114 forms a marker correlated with the coordinate system onthe anterior eye part of the subject eye. The input/output part 115 isan interface for outputting data and operation results of the aberrationamount, the origin of coordinates, the coordinate axis, the rotation andmovement of the coordinate axis, and the ablation amount to the surgicalapparatus. A display part 240 displays the optical characteristic of thesubject eye obtained by the measurement part 111 in relation to thecoordinate system formed by the coordinate setting part.

A surgical apparatus 300 includes a surgical control part 121, a workingpart 122, and a memory part 123. The surgical control part 121 controlsthe working part 122, and controls a surgical operation such as cornealrefractive surgery. The working part 122 includes a laser for thesurgical operation such as corneal refractive surgery. The surgicalmemory part 123 stores data for the surgical operation, such as dataconcerning cutting, a nomogram, a surgical schedule and the like.

Next, FIG. 7 shows a view (1) of experimental results by the eye opticalcharacteristic measuring apparatus of this embodiment. In thisembodiment, for the confirmation of measurement of eye opticalcharacteristics, 9 normal eyes, 24 keratoconic eyes, and 17 cataractouseyes were measured, and the half-value widths were obtained.Incidentally, in the drawing, the normal eye (normal) is indicated byrhombus (♦), the keratoconic eye (keratoconus) is indicated by square(▪), and the cataractous eye (cataract) is indicated by triangle (▴).

The measurement part 111 or the analysis part 111′ analyses the outputresult from the first received light signal (4) by a specified analyticmethod. That is, the blur of the received laser light is considered tobe the scattered light, and there is obtained the half-value width(square root of area for apots) on the basis of the size of the spotdiameter of the received light flux or the ratio of the maximum receivedlight amount of the received light flux to the minimum received lightamount, that is, the scatter intensity ratio (minimum intensity/maximumintensity, scattering coefficient) is obtained. Besides, the measurementpart 111 or the analysis part 111′ prepares the distribution (FIG. 6) ofthe spot diameter of the received light flux or the distribution of thescatter intensity ratio of the received light flux with respect to thephase (standard deviation) of the wavefront aberrations incident on thefirst light receiving part 23, which are obtained by the light receivingoptical system.

Incidentally, with respect to the cataractous eye, since it deviatesfrom the approximated straight line, it can be differentiated from thekeratoconic eye. That is, on the basis of the obtained straight lineapproximation, a test subject who is suspected of having the cataractouseye is discriminated, and this can be used as information for making adecision about the surgery and remedy.

FIG. 8 shows a view (2) of experimental results by the eye opticalcharacteristic measuring apparatus of this embodiment.

In this drawing, the correction by eq. (1) is added to the half-valuewidth of FIG. 7. The vertical axis indicates an amount obtained bysubtracting a value obtained by substituting the wavefront aberrationsof the lenslet into eq. (1) from the half-value width. Innon-cataractous eyes, obtained values are arranged substantiallyhorizontally. In the cataractous eye or an eye with large scattering,this value becomes large. Besides, a model eye whose scattering can beneglected is measured, and it is also conceivable that a correction isfurther performed by this measurement value to make the estimate of thescattering amount more accurate. Although the method used here issuitable for the measurement of the crystalline lens scattering, it isalso conceivable to apply this to measurement of retina scattering orthe like.

As the result of the analysis, as an example, there were obtained SIR(scatter intensity ratio)=0.460±0.067 for the normal eye,SIR=0.495±0.098 for the keratoconic eye, and SIR=0.667±0.148 for thecataractous eye (ANOVA (dispersion analysis), P<0.01). Besides, thescattering coefficient was 2.61±0.70 for the normal eye, 3.38±2.73 forthe keratoconic eye, and 10.13±7.25 for the cataractous eye. Besides,although there was no significant difference between the normal eye andthe keratoconiceye (P<0.122), there was significant difference betweenthe normal eye and the cataractous eye, and between the keratoconiceyeand the cataractous eye (P<0.01). Incidentally, 9 normal eyes withlittle scattering, 24 keratoconic eyes, and 17 cataractous eyes withlarge scattering were measured.

By this, possibility of measurement of the scattering amount by theHartmann-Shack wavefront sensor is suggested. After this, evaluationstandards comparable to visual functions are examined, and clinicaleffectiveness is confirmed.

Industrial Applicability

According to the present invention, it is possible to provide the eyeoptical characteristic measuring apparatus which enables the scatteringmeasurement by the Hartmann-Shack wavefront sensor whose main object iswavefront aberration measurement, and can accurately estimate the visualfunctions by performing the scattering measurement.

Besides, according to the invention, as the scattering measurementmethod by the Hartmann-Shack wavefront sensor, the scattering analyticmethod is developed in which the scattering amount is estimated from thescatter intensity ratio (SIR) of background light of the Hartmann image,and the eye optical characteristic measuring apparatus which can enablesimultaneous measurement of scattering by the optical system of theHartmann-Shack wavefront sensor can be provided.

Besides, according to the invention, the eye optical characteristicmeasuring apparatus can be provided which can make the judgment thatfrom the distribution of relations between the wavefront aberrations ofthe light flux incident on the light receiving optical system and thescattering degree of the received light flux, as the wavefrontaberrations of the light flux incident on the light receiving opticalsystem and the scattering degree of the received light flux become nigh,the influence of the cataract becomes large.

Besides, according to the invention, the eye optical characteristicmeasuring apparatus can be provided which can make the judgment thatfrom the distribution of relations among the wavefront aberrations ofthe light flux incident on the light receiving optical system, thescattering degree of the received light flux, and the spot diameter ofthe received light flux, as the wavefront aberrations of the light fluxincident on the light receiving optical system and the scattering degreeof the received light flux become high, or as the spot diameter of thereceived light flux becomes large, the influence of the cataract becomeslarge.

1. An eye optical characteristic measuring apparatus, comprising: alight source part for emitting a light flux of a specified wavelength;an illumination optical system for illuminating a minute area on aretina of a subject eye with the light flux from the light source part;a light receiving optical system for receiving a part of a reflectedlight flux which is the light flux emitted from the light source partand reflected by the retina of the subject eye, through a conversionmember for converting it into at least substantially 17 beams; a lightreceiving part for receiving a received light flux guided by the lightreceiving optical system to form signals; and an arithmetic part forobtaining wavefront aberrations of the light flux incident on the lightreceiving optical system and a scattering degree of the received lightflux on the basis of the signals from the light receiving part.
 2. Aneye optical characteristic measuring apparatus, comprising: a lightsource part for emitting a light flux of a specified wavelength; anillumination optical system for illuminating a minute area on a retinaof a subject eye with the light flux from the light source part; a lightreceiving optical system for receiving a part of a reflected light fluxwhich is the light flux emitted from the light source part and reflectedby the retina of the subject eye, through a conversion member forconverting it into at least substantially 17 beams; a light receivingpart for receiving a received light flux guided by the light receivingoptical system to form signals; and an arithmetic part for obtainingwavefront aberrations of the light flux incident on the light receivingoptical system and a spot diameter of the received light flux on thebasis of the signals from the light receiving part.
 3. An eye opticalcharacteristic measuring apparatus according to claim 1, wherein thearithmetic part obtains a distribution of relations between thewavefront aberrations of the light flux incident on the light receivingoptical system and the scattering degree of the received light flux. 4.An eye optical characteristic measuring apparatus according to claim 3,wherein the arithmetic part is constructed to judge that, as thescattering degree of the received light flux becomes high, an influenceof cataract or the like becomes large.
 5. An eye optical characteristicmeasuring apparatus according to claim 2, wherein the arithmetic partobtains a distribution of relations between the wavefront aberrations ofthe light flux incident on the light receiving optical system and thespot diameter of the received light flux.
 6. An eye opticalcharacteristic measuring apparatus according to claim 2, whereincrystalline lens scattering and retina scattering are estimated byremoving an influence of the wavefront aberrations from the obtainedspot diameter of the received light flux.
 7. An eye opticalcharacteristic measuring apparatus according to claim 2, whereincrystalline lens scattering and retina scattering are estimated by usingan approximate straight line based on measurement values of the spotdiameter of the received light flux of a normal eye or a non-cataractouseye, such as a keratoconic eye, and the wavefront aberrations forremoving an influence of the wavefront aberrations from the obtainedspot diameter of the received light flux.
 8. An eye opticalcharacteristic measuring apparatus according to claim 2, whereincrystalline lens scattering and retina scattering are estimated bycorrecting an approximate straight line based on measurement values ofthe spot diameter of the received light flux of a normal eye or anon-cataractous eye, such as a keratoconic eye, and the wavefrontaberrations, on the basis of a measurement value of a model eye in orderto form a scattering amount of the apparatus itself, for removing aninfluence of the wavefront aberrations from the obtained spot diameterof the received light flux.
 9. An eye optical characteristic measuringapparatus according to claim 5, wherein the arithmetic part isconstructed to judge that as the spot diameter of the received lightflux becomes large, an influence of cataract or the like becomes large.10. An eye optical characteristic measuring apparatus according to claim1, wherein the arithmetic part obtains a distribution of relations amongthe wavefront aberrations of the light flux incident on the lightreceiving optical system, the scattering degree of the received lightflux, and a spot diameter of the received light flux.
 11. An eye opticalcharacteristic measuring apparatus according to claim 10, wherein thearithmetic part is constructed to judge that, as the obtained wavefrontaberrations of the light flux incident on the light receiving opticalsystem and the scattering degree of the received light flux become high,or as the spot diameter of the received light flux becomes large, aninfluence of cataract or the like becomes large.
 12. An eye opticalcharacteristic measuring apparatus according to claim 3, furthercomprising a display part for displaying the distribution obtained bythe arithmetic part.
 13. An eye optical characteristic measuringapparatus according to claim 4, further comprising a display part or anoutput part for displaying or outputting a judgment result by thearithmetic part.
 14. An eye optical characteristic measuring apparatus,comprising: a light source part for emitting a light flux of a specifiedwavelength; an illumination optical system for illuminating a minutearea on a retina of a subject eye with the light flux from the lightsource part; a light receiving optical system for receiving a part of areflected light flux which is the light flux emitted from the lightsource part and reflected by the retina of the subject eye, through aconversion member for converting it into at least substantially 17beams; a light receiving part for receiving a received light flux guidedby the light receiving optical system to form signals; and an arithmeticpart for obtaining a point spread function obtained from wavefrontaberrations of the light flux incident on the light receiving opticalsystem and an actually measured spot diameter of the received light fluxon the basis of the signals from the light receiving part.
 15. An eyeoptical characteristic measuring apparatus according to claim 14,wherein the arithmetic part obtains a distribution of relations betweenthe point spread function obtained from the wavefront aberrations of thelight flux incident on the light receiving optical system and ascattering degree of the received light flux.
 16. An eye opticalcharacteristic measuring apparatus according to claim 14, wherein thearithmetic part is constructed to judge that, as a diameter of theobtained point spread function and/or the spot diameter of the receivedlight flux becomes high, an influence of cataract or the like becomeslarge.
 17. An eye optical characteristic measuring apparatus accordingto claim 14, wherein the arithmetic part obtains a distribution ofrelations between a diameter of the point spread function obtained fromthe wavefront aberrations of the light flux incident on the lightreceiving optical system and the spot diameter of the received lightflux.
 18. An eye optical characteristic measuring apparatus according toclaim 14, wherein crystalline lens scattering and retina scattering areestimated by subtracting a diameter of the point spread function fromthe obtained spot diameter of the received light flux.
 19. An eyeoptical characteristic measuring apparatus according to claim 2, whereinthe arithmetic part obtains a point spread function based on a signalfrom the light receiving part, and estimate crystalline lens scatteringand retina scattering by comparing the obtained point spread functionwith a point spread function obtained from the wavefront aberrations ofthe subject eye which are obtained on the basis of the signals from thelight receiving part.
 20. An eye optical characteristic measuringapparatus according to claim 2, wherein the arithmetic part obtains aminimum intensity and a maximum intensity in predetermined range with apoint image as the center, and obtains a Michelson contrast ratio or anarea at an intermediate point between the minimum intensity and themaximum intensity on the basis of this, and estimates crystalline lensscattering and retina scattering.